Polyamide and fibers derived therefrom



United States Patent 3,329,633 POLYAMIDE AND FIBERS DERIVED THEREFROMLawrence W. Crovatt, Jr., Raleigh, N.C., assignor to Monsanto Company, acorporation of Delaware No Drawing. Filed Oct. 15, 1964, Ser. No.404,187 4 Claims. (Cl. 260-18) ABSTRACT OF THE DISCLOSURE The lubricityproperties of polyhexamethylene adipamide fibers are improved byintroducing into the polymer between 0.1 and 5.0 weight percent of oleicacid dimer.

Fibers obtained from the homopolymer prepared from the reaction ofhexamethylene diamine and adipic acid (nylon 66) have obtainedcommercial importance and success. Although these fibers have much tocommend them, there is still need and room for new and improvedproperties. It is known that this commercial polyamide is very hard andcrystalline and quite difficult to handle in friction producingoperations. For this reason and because end-uses such as tire-cord,ropes and cordages are greatly benefited by a reduced yarn-to-yarnfriction, a permanent low-friction property as a characteristic of thepolymer is highly desirable.

Presently, in the commercial production of nylon 66 fibers, the as-spunfilaments are given a treatment to improve their lubricity and handlingproperties. This treatment usually consists of passing the filaments,while in the form of a bundle, through a bath of or over a wheel coatedwith the treating or finishing liquid. The finish, thus received by thefilaments, is nothing more than a coating and is not necessarily of apermanent nature. Most, if not all, of the lubricating agent containedWithin the finish bath, is often lost in subsequent processing of thefilament such as by mechanical handling, heating, washing, scouring anddyeing. If the finish does remain on the fiber until the finalend-product is produced, it

3,329,633 Patented July 4, 1967 terminator. Therefore, it is notnecessary to use undesirable polyamide cross-linking agents or vacuumfinish techniques in the polymerization reaction to keep the oleic aciddimer modified polyamide in a fiber-forming molecular weight range.Additionally, the more even distribution of the lubricity enhancingadditive throughout the polyamide chain results in a more uniform fiberlubricity and greater fiber strength.

The modified polyamides described herein are prepared by procedures wellknown in the art and commonly employed in the manufacture of unmodifiednylon 66 polymers. That is, the reactants are heated at a temperature offrom 180 C. to 300 C., and preferably from 200 C. to 295 C., until theproduct has a sufficiently high molecular weight to exhibitfiber-forming properties. This condition is reached when the polyamidehas an intrinsic often becomes less effective after the end-product isused for periods of time.

Therefore, what is needed is a lubricating agent of a permanent nature;one that is incorporated directly into the polymer and the filamentsproduced therefrom, in lieu of merely being coated on the outside ofthe. produced filaments. If an improvement of a permanent nature such asthis could be obtained, it would lead to significant reductions in yarnprocessing difficulties and subsequent increased end-product quality.Such an improvement would cause large reductions in fiber-to-fiberfriction and thus increase the maximum strength and'life obtainable intire cords, ropes and cordages.

Accordingly, it is an object of the present invention to provide amodified polyhexamethylene adipamide polymer and fibers producedtherefrom which possess high lubricity characteristics. 4

This and other objects and advantages will become apparent in the courseof the following detailed description of the invention and the claimsappended thereto.

In general, these objects are accomplished in accordance with thisinvention by adding a modifying agent to the polymer forming reactantsduring the course of polymerization. The modifying agent is oleic aciddimer and is used in an amount of from 0.1 to about 5.0 weight percentbased on the weight of the polyamide forming monomer, and preferablyfrom 0.1 to 2.0 weight percent.

Oleic acid dimer is an ideal modifying agent because it is a dibasicacid comonomer and is capable of being evenly distributed throughout thelong polyamide molecular chains. Also this additive does not causepolymer stabilization difiiculties because it does not act as a chainviscosity of at least 0.4, the intrinsic viscosity being in which N isthe relative viscosity of a dilute solution of the polymer in m-cresolin the same units at the same temperature and C is the concentration ingrams of polymer per cc. of the solution. The reaction can be conductedat superatmospheric, atmospheric or subatmospheric pressure. Often it isdesirable, especially the last stage of the reaction, to employ areduced pressure to aid in the removal of the reaction by-product.Preferably, the reaction is carried out in the absence of oxygen, e.g.,in an atmosphere of nitrogen. The hexamethylene diamine and adipic acidpolyamide forming reactants are normally introduced into the autoclaveas a preformed salt but may be in the form of uncombined diamine anddiacid when added. The modifying agent or additive should be added tothe polymerization reaction during the final polymer holding orfinishing cycle in order to avoid -undesirable polymer foaming. V

The modified polyamides as described herein may be prepared, spun anddrawn under conventional nylon forming production conditions. Inaddition to the aforedescribed additive, delustrants, anti-oxidants,plasticizers, viscosity stabilizers, chain terminators, and other likemodifying agents may be used in the preparation of the polyamides ofthis invention.

In order to illustrate the invention and advantages thereof with greaterparticularity the following specific examples are given. It is to beunderstood that they are intended to be only illustrative and are in noway intended to limit the invention. Parts and percentages are given byweight unless otherwise indicated.

EXAMPLE I A solution of 147 parts of hexamethylenediammonium adipate(nylon 66 salt) dissolved in 153 parts of water was added to a stainlesssteel evaporator which had previously been purged of air with purifiednitrogen. The evaporator was so positioned that the contents thereofcould be piped into a high-pressure autoclave when desired. The solutionwas then heated under a nitrogen blanket at a pressure of 13 p.s.i.g.with the continuous removal of steam as condensate until the solutionreached a temperature of 137 C. At this point the salt solution wascharged to a stainless-steel high-pressure autoclave which hadpreviously been purged of air by the use of purified nitrogen. Thetemperature and pressure were slowly raised until values of 220 C. and250 p.s.i.g., respectively, were reached. The temperature was thenfurther increased to 243 C. with the pressure being maintained at 250p.s.i.g. by the removal of steam as condensate. At this point thepressure reduction cycle egan. The pressure was gradually reduced toatmosheric over a 25 minute period. When the pressure reachedtmospheric, 0.5 weight percent (based on the weight of he polyamideforming monomer) of oleic acid dimer was added to the polymerizationreaction. The polymer nelt was then allowed to equilibrate for 30minutes at 278 C. This finished polymer had a relative viscosity If37.5.

The resultant polymer was melt spun directly from the aottom of theautoclave through a -hole spinneret to rield a white multi-filamentyarn. Upon being drawn this Iarn of 11.5 denier per filament exhibited atenacity of 3.0 grams per denier at an elongation of 24 percent.

EXAMPLE II In this example a solution of 147 parts ofhexamethylenediammonium adipate dissolved in 153 parts of water wasadded to a stainless steel evaporator which had previously been purgedof air by the use of purified nitrogen. The evaporator was positionedabove a stainless-steel high-pressure autoclave and equipped with meansfor dropping the contents thereof into the autoclave when desired. Thissolution was then heated under a nitrogen blanket at a pressure of 13p.s.i.g. with the continuous removal of steam as condensate until thesolution reached a temperature of 137 C. At this point the salt solutionwas charged to the autoclave. The temperature and pressure in theautoclave were slowly raised until values of 220 C. and 250 p.s.i.g.,respectively, were reached. The temperature was then further increasedto 243 C. and the pressure was maintained at 250 p.s.i.g. by thecontinuous removal of steam as condensate. At this point the pressurewas gradually reduced to atmospheric during a 25 minute period; at theend of which 1.0 weight percent (based on the weight of polyamideforming monomer) of oleic acid dimer was added to the polymer melt bymixing and stirring over a period of 30' minutes during which thetemperature was maintained at 278 C.

The final finished polymer of 38.3 relative viscosity was melt extrudeddirectly from the bottom of the autoclave through a 10-hole spinneret toyield a white multifilament yarn. The yarn was godet drawn over a hot(90 C.) pin to yield filaments having a 10.7 denier per filament, atenacity of 7.5 grams per denier, and an elongation of 27 percent.

The filaments obtained in the above examples were closely examined andcompared with filaments obtained from the standard, unmodifiedpolyamide, nylon 66. The filaments of this invention exhibited a muchmore waxy or lubrid feel to the hand than those prepared from thestandard, unmodified nylon 66 polymer. Additionally, a high degree oflubricity was evidenced by the ability of the fibers to slide freelyover one another in bundles.

As previously noted, the products obtained in the practice of thisinvention are particularly useful in the manufacture of tire cords,ropes and cordages, where polyamide filaments having low fiber-to-fiberfriction are especially desirable. The products obtained in the practiceof this invention may also be used to advantage in the manufacture offabrics, film, and the like where the ultimate end-use intended would bebenefited by the employment of a polymer having high lubricitycharacteristics.

This improvement in lubricity has been obtained without degradation ofother physical properties. That is to say, physical properties such astenacity, elongation, and relative viscosity of the fibers produced inaccordance with this invention have been maintained at the samedesirable levels as those exhibited by the standard commerciallysuccessful polyamide nylon 66.

As many widely diiferent embodiments of this invention may be madewithout departing with the spirit and scope thereof it is to beunderstood that the invention is not to be limited by the specificembodiments set forth herein but only by the claims which follow.

Having thus described my invention in detail what I claim as new anddesire to secure by US. Letters Patent is:

1. A fiber-forming synthetic linear polyamide having improved lubricitywhen in fiber form which comprises the product obtained by reacting at atemperature of between C. and 300 C. reactants comprising, (A) apolyamide forming monomer consisting of the salt formed by substantiallyequimolecular proportions of adipic acid and hexamethylene diarnine, and(B) from 0.1 to about 5.0 weight percent based on the weight of the (A)of the additive oleic acid dimer.

2. The fiber-forming synthetic linear polyamide as set forth in claim 1,wherein said additive is present in an amount of from 0.1 to 2.0 weightpercent based on the Weight of the polyamide forming monomer.

3. A textile fiber comprising the polyamide as defined in claim 2.

4. A fiber-forming synthetic linear polyamide having improved lubricitywhen in fiber form which comprises the product obtained by the processcomprising polymerizing a polyamide-forming monomer consisting of thesalt formed by substantially equimolecular proportions of adipic acidand hexamethylene diamine and adding to the polymer during the finalpolymerization stage thereof, from 0:1 to about 5.0 weight percent ofoleic acid dimer.

References Cited UNITED STATES PATENTS 3,240,732 11/1966 Ham et al260-18 DONALD E. CZAIA, Primary Examiner.

LEON J. BERCOVITZ, Examiner.

C W. IVY, Assistant Examiner.

4. A FIBER-FORMING SYNTHETIC LINEAR POLYAMIDE HAVING IMPROVED LUBRICITYWHEN IN FIBER FORM WHICH COMPRISES THE PRODUCT OBTAINED BY THE PROCESSCOMPRISING POLYMERIZING A POLYAMIDE-FORMING MONOMER CONSISTING OF THESALT FORMED BY SUBSTANTIALLY EQUIMOLECULAR PROPORTIONS OF ADIPIC ACIDAND HEXAMETHYLENE DIAMINE AND ADDING TO THE POLYMER DURING THE FINALPOLYMERIZATION STAGE THEREOF, FROM 0.1 TO ABOUT 5.0 WEIGHT PERCENT OFOLEIC ACID DIMER.